AT THE MOMENT OF CHEMICAL CHANGE. 
761 
view it is necessary to suppose that the present elemental atoms are susceptible of 
a yet further division*. 
These ideas, however philosophical and suggestive, are yet, it must be allowed, very 
hypothetical. The proof of the compound nature of a chemical substance is of a very 
simple kind. It lies in the fact, that it has been made by the composition of certain 
parts, or broken up into those parts, or at least in some phenomena which are sup- 
posed to be the evidence of this. Indeed the rational formula of a chemical sub- 
stance is but a memorandum of its reactions, and a particular mode of expressing 
the law of the synthesis and analysis of the body, apart from which it has but little 
meaning. The true nature therefore and chemical formula of the elemental bodies, 
as of all other substances, is to be discovered by the study of the series of che- 
mical changes in which they are formed, and by the phenomena which they pre- 
sent when they pass into the combined condition. There are even well-known facts 
of great importance in this point of view, some unexplained, and some, I conceive, 
misinterpreted. 
The point which I shall seek to establish is this, — that at the moment of chemical 
change a chemical difference exists between the particles of which certain elemental 
bodies consist, perfectly the same in kind to that which exists between the particles 
of compound substances under similar circumstances, and on which the phenomena 
of combination and decomposition depend. That a peculiar chemical relation exists 
between two particles which combine, is generally admitted and expressed by the 
term affinity. The electro-chemical theory has defined more exactly in what this 
affinity consists, and states that the two particles are to one another in a positive and 
negative electric relation. But I do not know that it has ever been pointed out that this 
chemical relation — this affinity between the particles of a substance — is an essential 
condition of the decomposition as well as of the eomposition of the body. As I am 
about to infer a chemieal difference between the particles of the element from the 
faet of their chemical separation, I must say a few words upon this point, and I shall 
simplify the whole question by stating briefly the mode in which I consider ehemical 
change to be effected. I may do this sufficiently for my present purpose in the fol- 
lowing propositions: — 
1. That when two particles chemically combine, a certain chemical relation exists 
between them which is expressed by the terms positive and negative. The che- 
mical difference of the particles I term the difference between their conditions in 
this respect. 
2. That when chemical combination takes place between the particles of which any 
two or more substances consist, a chemical difference exists between the particles of 
each substance, so that the particles of the same substance are to one another in a 
positive and negative relation. 
3. That the chemical relation between any two particles of these substances is 
* Comptes Rendus des Travaux de Chimie, August 1 849. 
MDCCCL. 5 E 
